Increasing receptivity for acid dyes

ABSTRACT

Dye receptivity of fibers used in the dyeing and printing of cationic dyeable nylon as used as carpet fibers or similar polymers difficult to dye with anionic dyes are improved by a coating rendering these fibers more receptive to anionic dyes.

This invention relates to treating fibers used in the dyeing and printing of cationic dyeable nylon as used in carpet fibers or similar polymer difficult to dye with anionic dyes to render the cationic dyeable fibers more receptive to anionic dyes.

BACKGROUND

Various polymers such as cationic dyeable nylon used as a carpet fiber are difficult to dye and have reduced uptake of anionic dyes as compared with acid dyeable nylon.

Nylon carpet fiber is generally classified as to type, depending upon the nylon's receptivity to acid or anionic dyes and basic or cationic dyes. Cationic dyeable nylons contain within the polymer structure sufficient SO₃H groups or COOH groups (which groups are receptive to cationic or basic dyes) to render the nylon fiber dyeable with cationic dyes. Acid dyeable nylons are essentially conventional nylons, such as polyhexamethylene adipamide and polycaprolactam. Acid dyeable nylons vary as to type and are characterized as being weakly dyed with acid dyes, average dyed with acid dyes, or deeply dyed with acid dyes.

The advantages of employing the inherent acid type stain resistance of cationic dyeable nylon fibers, particularly when used in carpets and floor coverings, and dyed to the appropriate shade with anionic dyes at pH of about 2.0 to about 6.5 are described in earlier patents to Jenkins such as U.S. Pat. Nos. 5,085,667; 5,199,958; 5,350,426; 5,354,342; 5,466,527; 5,571,290; 5,912,409 and 6,013,111, the disclosures of which are hereby incorporated by reference. As used herein anionic dyes includes acid dyes and premetallized acid dyes. These carpets are known commercially as Duracolor® (Lees/Mohawk).

Cationic dyeable nylons generally exhibit inherent stain resistant properties, especially to acid-type stains found in many colored drinks and other food products, as compared to other nylon types used for carpet. However, while useful this resistance to acid dyes reduces the uptake of acid dyes in manufacturing when compared to acid dyeable nylon.

DESCRIPTION OF THE INVENTION

The present invention includes providing a coating on a difficult to dye polymeric substrate such as cationic dyeable nylon fibers that renders the polymeric surface receptive to anionic dyes, followed by application of an anionic dye or dyes. In the case of carpets treating the cationic dyeable nylon fibers to make them receptive to acid dyes allows heavier shades to be developed than with previous procedures and affords carpets with further choices in style and in particular shade. When applied to either yarn or carpet constructed of cationic dyeable nylon fibers, increased shade is developed. The treatment may be applied to either yarns before being made into carpets or to carpet fabrics, either undyed or predyed with anionic dyes. Dyeing or an additional dyeing step, as the case may be, with an acid dye occurs after the fibers are treated. The stain resistance of the treated yarns/carpets is not diminished because the dye sites created by the treatment process contain all the acid dyes from the subsequent dyeing.

The invention includes a process for imparting increased receptivity for acid dyes to the surface of cationic dyeable nylon fibers by applying to the nylon fibers a cationic polymer that enhances the fiber's receptivity to acid dyes by establishing dye sites on the nylon fibers. The coatings are applied with any of the conventional means for finishing and/or dyeing fibers, yarns or carpets, as the case may be.

The process of the invention may also be carried out on other polymers that are themselves not normally acid dyeable such as polyvinyl chloride (PVC) and polypropylene (PP) as well as polyester. When constructed into carpets treating polymers of this group will produce carpets with these polymers as wear surfaces that are acid dyeable.

A coating or finish is applied to the polymer surface for which enhanced anionic dye acceptance is required with a coating material that improves anionic dye receptivity. Materials suited for this task are group of cationic polymers exhibiting the ability to bond to the cationic dyeable polyamide, PVC, polypropylene or polyester, yet provide anionic dye sites for subsequent coloration. These materials may or may not be cross-linkable. For some performance purposes it may be necessary to crosslink the materials and form a matrix or network on the surface of the cationic dyeable polyamide. The degree of increase in anionic dyeability has been measured by spectrophotometry to be up to 100% or greater (200% of the control), but may be higher. The governing factor is the balance between the acid dyeability and stain resistance desired in the final product.

The coating or finish may be applied by any convenient means used in the art including pad bath, spray, various printing techniques including roller printing, screen printing, space printing as can be accomplished with Belmont, Superba and other similar yarn printers in the trade, ink jet printing, injection printing such as Chromojet printing.

A preferred group of polymers are those of the TruDot® (MeadWestvaco, Special Products Group, Charleston, S.C.) including TruDot® P-2673 swellable latex, a cationic styrene-acrylic copolymer available as a water-based swellable cationic latex (copolymer 33-37%, water 63-67%) designed for printing and inkjet coating formulations with inkjet receptivity on nonporous and porous surfaces. The use of a crosslinker such as XAMA 220 (a polyfunctional aziridine compound from Bayer) up to 12-15% is recommended. The polymer is hydrophobic and the use of a crosslinker reduces hydrophilicity. Also available is TruDot® P-2615 cationic solution polymers (MeadWestvaco) a cationic acrylic copolymer (27-33%) in water (67-73%) (clear liquid) developed for use as low molecular weight binders in inkjet print formulations.

Other dye receptive coatings to consider include styrene maleic anhydride imide resin (SMA) available from Sartomer USA. Also, maleic anhydride modified adhesives for coating have shown improved adhesion to nylon than the non-modified adhesive. Quaternary based polymers such as poly-diallyl dimethyl ammonium chloride (poly-DADMAC) (LPM Technologies) should be considered as creating acid dye sites on cationic fibers.

EXAMPLE

Increased acid dyeing levels have been achieved by applying an anionic dye receptive coating to cationic dyeable nylon yarn. A solution of the cationic styrene acrylic copolymer TruDot® P-2673 (1% to 7.5%) with a corresponding amount of crosslinking agent XAMA® 220 (0.6 to 0.1%) was applied in a space dyeing machine (without dye). The coated yarns were tufted into carpet. Acid dyes, specifically premetallized acid dyes were applied from a bath containing the dyes and necessary dye auxiliaries at 600% wet pick up on the weight of the carpet. The carpet was steamed for 8 minutes in a lab steamer simulating a saturated steamer on a continuous carpet dye range. Cold tap water was used to rinse any residual dye and chemical from the carpet, followed by drying. The resulting carpet exhibited a multi-tone appearance and deeper shade than the control fabric. 

1. A process for increasing the receptivity of cationic dyeable nylon fiber or other difficult to dye polymer fiber to acid dye comprising: (1) applying to the fiber a cationic polymer coating that is receptive to acid dye and provides anionic dye sites for subsequent coloration, and thereafter (2) applying an acid dye or premetallized acid dye to the thus treated polymer and dyeing the fiber.
 2. The process of claim 1 wherein the fiber is a cationic dyeable nylon.
 3. The process of claim 1 wherein the fiber is polyvinyl chloride, polypropylene, polyester or combinations of two or more of these.
 4. The process of claim 1 in which the receptivity-improving polymer is a cationic styrene-acrylic copolymer.
 5. The process of claim 1 in which the receptivity-improving polymer is a cationic acrylic copolymer.
 6. The process of claim 1 in which the receptivity-improving polymer is a styrene maleic anhydride imide resin.
 7. The process of claim 1 in which the receptivity-improving polymer is a maleic anhydride adhesive polymer.
 8. The process of claim 1 in which the receptivity-improving polymer is a poly-diallyl dimethyl ammonium chloride.
 9. The process according to claim 1 wherein in step (2) the fibers are dyed with an acid dye or a premetallized acid dye at a pH of from about 2.0 to about 6.5 and thereby fixing dye to the fibers.
 10. The process according to claim 1 wherein in step (2) the fibers are dyed with an acid dye or a premetallized acid dye at a pH of from 2.0 to 6.5 to impart a pre-requisite depth of shade to the nylon fibers, and an additional step of (3) heating the dye-laden fibers to fix the dye into the fibers.
 11. The process of claim 1, in which the cationic dyeable nylon fibers contain SO₃H and/or COOH groups receptive to cationic or basic dyes.
 12. The process of claim 1, in which, subsequent to dye fixation, a fluorocarbon soil repellant is applied to the fibers.
 13. A method of increasing the receptivity of cationic dyeable nylon fibers to acid dye comprising (1) applying to the nylon fibers a cationic acrylic polymer or cationic styrene-acrylic polymer receptive to acid dye, and thereafter (2) dyeing the treated fibers of step (1) with an acid dye.
 14. The process of claim 13 in which the fibers are in the form of a yarn.
 15. Nylon carpet having improved stain resistance composed of fibers comprised of a cationic dyeable nylon treated with a cationic polymer acid dye receptivity agent then dyed at a pH of from about 2.0 to 6.5 with an acid or premetallized acid dye.
 16. A process for increasing the receptivity of cationic dyeable nylon fiber or other difficult to dye polymer fiber to acid dye comprising: (1) applying to the fiber a cationic polymer coating that is receptive to acid dye, and provides anionic dye sites for subsequent coloration, and thereafter (2) applying an acid dye or premetallized acid dye to the thus treated polymer and dyeing the fiber, wherein the fibers treated in step (1) have an increase in anionic dye dyeability, when measured by spectrophotometry, up to 100% or greater as compared to fibers not subjected to treatment prior to step (2).
 17. The process of claim 16 in which the increase in anionic dye dyeability, when measured by spectrophotometry, is at least 100% as compared to fibers not subjected to treatment prior to step (2). 